Atopic dermatitis (AD) refers to chronic and recurrent inflammatory skin manifestation showing pruritus, and is mainly observed in infants and children. Atopy is the most representative allergic disease together with allergic rhinitis and bronchial asthma, while it has been known that the atopy prevalence rate is 10-30% in children and 1-3% in adults.
Atopic dermatitis occurs due to a hypersensitive reaction of the immune system against antigens, such as dust mites, invading the body. The antigens are delivered to T cells through macrophages, while the T cells differentiate into Th1 or Th2 cells according to the type of antigens or receptors reacting therewith. Th2 cells activate humoral immunity through cytokines, such as IL-4, IL-5, and IL-10, and activate B cells, leading to increased IgE production and thus causing atopic dermatitis. Whereas, Th1 cells activate cellular immunity through IL-12 and IFN-γ, and IFN-γ inhibits the production of IgE. Therefore, the balance of the immune regulation of Th1 cells and Th2 cells is maintained to relieve atopic symptoms.
Although there is still no definitive treatment method for atopic dermatitis, anti-allergic drugs, anti-histaminic drugs, steroids, and other medicines are used therefor. Of these, steroids, which have been the most frequently prescribed one in an ointment formulation for treating atopic dermatitis, degrade immune responsiveness to reduce inflammation, while being reported to cause various types of side effects upon their long-term use.
Meanwhile, many lactic acid bacteria or dairy products containing lactic acid bacteria are being marketed as food materials having an immune regulatory action. Examples of the lactic acid bacteria may include Lactobacillus genus, Lactococcus genus, Streptococcus genus, Pediococcus genus, Enterococcus genus, and the like, and these lactic acid bacteria are known to have immunopotentiating or anti-allergic action. The present inventors were granted a patent right for Lactobacillus rhamnosus IDCC 3201 having a balanced immunoregulatory function of Th1 and Th2 cells, which is a novel strain material having no side effect upon being used for a long period of time and is capable of treating atopic dermatitis fundamentally (Korean Patent Registration No. 1007429000000).
However, 100 trillion or more enteric bacteria of approximately 500 different types are living in the human intestines, while harmful bacteria, such as E. coli, and beneficial bacteria, such as lactic acid bacteria, are maintained in a balanced manner as resident flora. Therefore, the administered lactic acid probiotics possess a limited capacity in their competitive adherence to the intestinal mucosa, and thus the effect thereof has been varied depending on their adhesion rate. In addition, certain number of lactic acid probiotic bacteria are killed during their passage of the gastrointestinal tract or dropped out of the adhesion competition and then are discharged together with defecation. Thus, the lactic acid probiotic bacteria have a limitation in their contribution to the treatment of severe atopy.
Moreover, probiotics need to be taken in a more excessive administrative manner than their standard counts so as to improve the efficiency of their adhesion to the intestinal mucosa, while being required to pass many obstacles in the body prior to their arrival at the intestines. Thus, the microbial intake count and the treatment efficiency of atopy are difficult to predict. Due to these problems, there are few lactic acid bacteria that exhibit the same level or treatment efficiency as steroid-based drugs. Despite efforts to improve the efficacy of probiotics in a composite formulation, there have been problems in that the normalized level for the effect of probiotics is unable to be established since the death of probiotic bacteria strains naturally occurs over time during their storage.
As studies about the human intestinal mucosal immune system have been recently progressed, there have been reports about the interaction and adhesive strength between intestinal mucosal immune cells of a human being as a host and cellular wall components of lactic acid bacteria. Of these, toll-like receptor-2 (TLR-2) of dendritic cells (DC) binds with lipoteichoic acid and peptidoglycan existing in the cellular wall of said bacteria to deliver immune-related signals.
In addition, the lactic acid bacteria having immunoregulatory functions achieve extracellular production of short chain fatty acid (SCFA) and immuno proteins when fermented in specific and distinct media, thereby promoting the secretion of IFN-γ and IL-12 from Th1 cells and thus leading to the alleviation of atopic dermatitis. However, while most products fermented with lactic acid bacteria do not alleviate atopic dermatitis, only some selective lactic acid bacteria produce these substances, and thus the value of developing such bacteria is high.
Under these backgrounds, the development of a composition is required that is useful to treat atopic dermatitis more fundamentally by overcoming the side effects of steroid-based drugs used for atopic dermatitis and the limitation of the lactic acid probiotics in the treatment of atopic dermatitis due to their adhesion rate.